Gantry



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FRED L. WHITE ATTORNEY United States Patent GANTRY Fred L. White, Marion, Ohio, assignor to The Osgood Company, Marion, Ohio, a corporation of Ohio Application May 20, 1953, Serial No. 356,217

2 Claims. (Cl. 21259) In a portable equipment of this nature, it is necessary to keep the overall dimensions within certain limits so that the equipment can be moved readily from one work location to another. For instance, the height of these machines must. be kept as low as possible to clear under wires, bridges, and other overhead obstructions. moving such portable equipment it is customary to lower the boom until the point of the boom is no higher than the cab, and to have nothing on the machine projecting above the cab.

It is also desirable to keep the angle between the boom and the boom supporting ropes at the maximum in order to keep down the stresses in both. The longer the boom, as in the case of portable cranes, the more acute this angle becomes.

In some cases a so-called back hitch gantry is used in an effort to secure the maximum angle between the boom and the boom supporting ropes. Here, the main gantry is built at the extreme rear of the deck of the crane and the boom hoist ropes are attached either directly, or through bars or ropes, to this gantry. This construction is satisfactory when the boom is up in working position, especially at high angles, as then there is a maximum angle between the boom and the boom supporting ropes. However, since the ropes and the bars or ropes to which they are attached follow a line between the boom point and the top of the back hitch gantry, when the boom is lowered until the point of the boom is even with, or below the top of, the gantry, the angle between the boom and the ropes becomes quite acute. As a result, then the stresses in both the boom and the ropes, even with no load on them, are greater than when the machine is fully loaded with the boom at a high angle.

In other cases the gantry has been used to support the drum and other machinery, and the gantry has been placed more nearly in the center of the crane or other portable equipment. With this design, the angle between the boom and the ropes is less than where a back hitch gantry is used, and, of course, the stresses are greater. To

help to increase the angle between the boom and the' higher than a 50 angle, then the advantage is with the back hitch gantry. On the other hand, when an extended or high auxiliary gantry is used, and the boom is lowered to cab height or below, the angle between the boom and the ropes is still much greater than with a back hitch gantry. 7

There is no advantage, however, in lowering the boom to cab height to get overhead clearance if the extended gantry is kept in its high position, since this extends the gantry from four to ten feet above the top of thecab. To offset this condition, the extended gantries in most cases have been designed to be lowered to cab height. Generally this is accomplished by removing pins from the back legs of the extended gantry and allowing the extended gantry to lean ahead'until flush with the top of the cab. This makes it unnecessary to disconnect the boom support ropes, but it is necessary to attach stay ropes from the top of the extended gantry to the topof' thestandard gantry in order to support the weight of the boom.

Some extended gantries have been arranged to fold down like a pantograph; and screws, or fluid-pressure operated pistons have been used for this purpose. However, such extended gantries as have been heretofore designed to be folded or lowered, while carrying the boom, require not only the operator of the crane but also two or three additional men on the roof of the crane to lower them. Pins have to be removed and stay ropes have to be connected. In again raising the gantry, the process must be reversed; and again men are needed on the roof to remove the stay ropes and insert the pins. The whole process of raising or lowering the gantry requires one or more extra men and from fifteen minutes to an hour or more to accomplish. One object of this invention is to provide a gantry which can be raised or'lowered simply by the operator of the crane working alone.

A further object of the invention is to provide a gantry which can be raised or lowered without having to remove or replace any pins or ropes.

A further object of the invention is to provide a gantry of the type described which can be operated in either high or low position, or in any position between.

Another object of this invention is to provide a gantry which can be raised or lowered with the boom in any position. 7

Another object of the invention is to provide a gantry so constructed that the boom can be lowered to cab height or below while the gantry is still in raised position, and so constructed that the gantry can be raised to operating position before raising the boom from the ground or below cab height. This cannot be done with any gantry heretofore known.

Still another object of the invention is to provide an auxiliary gantry of the character described which can also be used to raise and lower the counterweight of the machine;

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.

In the drawings:

Fig. 1 is a side elevation showing the frame of a portable crane equipped with a standard gantry and with an auxiliary folding type gantry built according to one embodiment of this invention, the auxiliary gantry-being shown in full lines in extended position and in dotted lines in folded position, the cab of the crane being shown also in dotted lines;

Fig.2 is a fragmentary plan view showing the'standard gantry and the strut of the folding gantry, the cab of the crane being shown in dotted lines;

. Fig. 3 is a side elevation of a mobile crane equipped Patented Dec. 18, 1956 with an auxiliary gantry built according to another embodiment of this invention, the auxiliary gantry being shown in partially raised position, and the boom being shown in full lines in lowered position and in dotted lines in partially raised position;

Fig. 4 is a view on an enlarged scale showing the auxiliary gantry folded down to its lowered position, the boom ropes being omitted for the sake of clearness in illustration;

Fig. 5 is a view on the same scale as Fig. 4 but showing the auxiliary gantry in the position of Fig. 3;

Fig. 6 is a view on a corresponding scale, but showing the auxiliary gantry extended by means of an auxiliary piston rod to its full height;

Fig. 7 is a section showing the fluid-pressure operated piston and cylinder used in the auxiliary gantry of Figs. 3 to 6 inclusive, and showing the positions of these parts when the auxiliary gantry is in completely folded position;

Fig. 8 is a similar section showing the piston extended to an intermediate position;

Fig. 9 is a similar section showing the piston extended to its fully extended position through use of the auxiliary rod;

Fig. 10 is a plan view, similar to Fig. 2 showing the modified form of auxiliary gantry;

Fig. 11 is a more or less diagrammatic view showing how the foldinggantry of Figs. 1 and 2 may be used to lift the counterweight from the crane; and

Fig. 12 is a rear view showing the counterweight and lifting attachment.

Referring first to the embodiment of the invention shown in Figs. 1 and 2, denotes the upper body or cab of a portable self-propelled hoist or crane that is rotatably mounted on a suitable chassis (not shown). The frame or deck of the crane is denoted at 22. A boom 23 is pivotally connected at its lower end to the deck 22 in conventional manner- Secured in conventional manner to the frame or deck 22 is a conventional or low gantry such as is commonly used for shovel and short boom operations. The boom support ropes are attached to the top of this gantry for such operation. This gantry comprises a pair of spaced parallel uprights 24 and a pair of rods or bars 25. Bars 25 are connected at their lower end to the deck or frame and at their upper ends to the uprights 24.

The auxiliary gantry of the present invention is telescopically adjustable and comprises a strut 28 which is pivotally connected to the top of the standard gantry by the pin or tie rod 27. The strut 28 extends toward the .rear of the cab. Pivotally connected by means of straps 30 to the deck 22 at the rear thereof are a pair of spaced, parallel cylinders 32. Mounted to reciprocate in each of the cylinders 32 is a piston to which is secured a piston rod 34. The piston rods 34 are pivotally connected by means of a pin or tie rod 35 to the strut 28 adjacent the rear end thereof. The boom hoist ropes 37 operate over a sheave 38 carried on the pin 35. These ropes may be connected through a sheave 39 and a cable 40 to the boom; and sheave 39 is connected by ropes 41 to the sheave 42 and drum 44.

The gantries are mounted in a central well or opening between the sides of the cab.

in Fig. l the auxiliary gantry is shown in extended position. When the piston rods 34 are retracted, as shown in dotted lines, the pin 35 connecting the piston rods with the strut 28 is the same horizontal plane with the pin 27 in the top of the low gantry, which is below the maximum height of the cab. When the auxiliary gantry is in folded position, therefore, it does not project above the cab and will, therefore, readily clear wires, bridges, and other overhead obstructions. When pressure is applied to the underside of the pistons, the rods 34 are raised, and rock the strut 28 upwardly about the axis of the low gantry pin 27, raising'the auxiliary gantry to the maximum height allowed by the cylinders. The upper cylinder walls in this instance act as safety feans.

When the auxiliary gantry is in its high position, each piston is in contact with the upper end of its cylinder, and no hydraulic or pneumatic pressure is required to maintain it there. If the machine is operated with the auxiliary gantry in an intermediate position, the pressure would be placed on the upperside of the pistons to support the pistons in such intermediate position, but if there should be failure of a supply line, or leakage of a packing, the only thing that would happen would be that the pistons would move up into contact with the upper cylinder walls and lower the boom slightly.

The auxiliary gantry illustrated can be raised before the boom is raised and lowered after lowering of the boom. Furthermore, no additional help is required by the operator of the crane; and nothing need be added or be removed in order to raise or lower the gantry. In operation, too, as will be clear from Fig. 1, the angle between the boom supporting ropes is increased over what would be attainable if only a conventional, low gantry were used. All of the advantages of the back hitch gantry for high angle boom operation and all of the advantages of the extended type of gantry for low boom operation are secured.

The piston may be operated either by hydraulic or pneumatic pressure. The supply and exhaust lines to the cylinder have been omitted for the sake of clearness. It is necessar of course, to provide a hydraulic pump or an air compressor on the crane, to operate this gantry. Also a conventional double-acting or three-way type of valve for admitting pressure fluid to one end or the other of the cylinders is required. The pump might be either power or manually operated. The pressure required to either raise or lower the auxiliary gantry is quite low.

Referring now to the telescopically adjustable type of auxiliary gantry shown in Figs. 3 to 10 inclusive, 60 denotes the upper body of a portable self-propelled hoist that is rotatably mounted on a'suitable mobile chassis 61 which includes either endless track type traction members, or wheel mounts, a suitable prime mover, and controls therefor (not shown) in the upper body as is customary in the art. The frame or deck of this mobile crane is denoted at 62. The boom 63 is pivotally supported on the deck 62 in conventional manner. Secured to the deck 62 within a central well in the cab 60 are a pair of struts 64 which extend upwardly and rearwardly from the deck 62. Vertically extending rods 65 are secured at their lower ends to the deck 62 and at their upper ends to the struts 64. Struts 64 and rods 65 constitute a standard or low gantry, the rods 65 forming the back legs thereof.

Pivotally secured to the low gantry by means of the rod 67 is a strut 68. Pivotally mounted upon the deck 62 between the boom 63 and the low gantry and in parallelism to each other are a pair of cylinders 72. Pistons 73 (Fig. 7) reciprocate in these cylinders and are provided with piston rods 74 which are pivotally connected by means of the pin or rod 75 with the forward end of the strut 68. The boom hoist ropes 77 operate over a sheave 78 (Fig. 4) that is mounted upon the rod 75. They are connected to the boom through a conventional sheave 79 and cable 80. Sheave 78 is connected by rope 81 and sheave 82 with the drum 84. Sheav-e 82 is mounted upon the pin or rod 67.

In this embodiment of the invention the piston rod 74 is made in two telescoping sections, the portion which is connected to the piston 73 being tubular and being denoted at 74; and this portion being adapted to telescopingly receive a rod section 74'.

In Figs. 4 and 7 the piston rod is shown fully collapsed. In this position the auxiliary gantry is lowered to below cab height; and the pivot rod or pin 75 is on the same horizontal level as the pivot pin 67. When pressure is applied to the lower end of the piston 73 the auxiliary gantry is raised until it is in the position shown in Fig. 5. This is as far as the auxiliary gantry can be raised by power. If the boom is raised to a high angle, the loose piston section 74' is simply pulled part way out of the piston rod 74. In effect, then, the strut 68 and piston rod section 74' constitute a simple back hitch gantry. The cylinder 72 is shaped so as to have a shoulder 77 (Fig. 9) to limit the outward movement of the piston rod 74; or some other form of suitable stop may be pro vided to so limit the outward movement of the piston rod. This is to insure overlap of the cylinder on the piston rod to prevent buckling under load.

The gantry of Figs. 3 to 10 inclusive has the same advantages as the gantry of Figs. 1 and 2, but is designed for use on a machine with different machinery arrangements on the deck.

In the case of the gantry of Figs. 1 and 2 the boom radius can be varied by changing the length of the projection of the piston rod 34 out of the cylinder 32 thereby giving close adjustment on the boom. Other gantries have been built using adjustable legs but in these the adjustment could only be effected by pulling the gantry up or lowering it by ropes and locking it in position with pins or bolts. With the present invention it is possible to get an adjustable height or length of leg using fluid-pressure operated means to accomplish this. This permits of operating in any position and is not dependent upon fixed positions.

A further use of the fluid-pressure operated folding gantry is shown in Figs. 11 and 12. It is customary to use a counterweight at the rear end of the upper body of a portable crane and similar equipment to counterbalance the boom when extended. Such a counterweight may weigh as much as sixteen thousand pounds or more. In moving the machine over the road on a trailer, it is necessary to remove this counterweight and to transport it in a separate truck because the excessive weight of crane plus counterweight would not be allowed on the road. It has heretofore been quite a problem to remove this heavy counterweight from the machine prior to the transportation of the machine, and to replace it after the machine is in its new location, without use of another crane.

With the present invention it is possible to use the fluid power which operates the auxiliary gantry to raise this counterweight from its working position and move it into position Where it can be lowered upon a truck. For this purpose the side arms of the strut 28 have been extended rearwardly of the pivot pins as denoted at 90 (Figs. 11 and 12) so that they can receive pins 91 by which the upper loops 92 of cables 94 may be connected to the strut 28. The loops 95 at the lower ends of these cables may in turn be connected by pins 96 to the screw eyes 98 that are fastened in the upper face of the counterweight 100. To remove the counterweight from its normal working position the deck is swung crosswise of the crawlers or endless traction members; and the truck or trailer which is to receive the counterweight is backed under the rear of the deck. The strut 28 is then partially lowered and the cables 94 are attached to the strut and to the counterweight. The strut is then raised slightly by hydraulic or pneumatic power, as the case may be, thus lifting the counterweight; and the locking or shear bars 99, by which the counterweight is secured, in position are removed. The strut 28 is then lowered by exhausting the oil or air from the lower portion of the cylinders 32 and the counterweight is thus lowered onto the truck or trailer. When reinstalling the counterweight the above procedure is reversed. The counterweight is not permanently supported by the strut 28 but rests normally on the shear bars in the end of the deck. It is only attached to the strut when being removed or installed.

This provides a dual use for the cylinders 32. They can be used to alter the height of the auxiliary gantry and for lifting or lowering the counterweight.

While the invention has been described in connection with different embodiments thereof, it will be understood that it is capable of further modifications; and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. A machine of the character described having a chassis, a frame pivotally mounted on said chassis for rotation about a vertical axis, a boom pivoted at one end to said frame at one side of said axis, and having its opposite end free, a counterweight removably mounted on said frame at the opposite side of said vertical axis from said boom, a gantry fixedly secured to said frame, a cylinder pivotally connected at its lower end to said frame, a piston reciprocable in said cylinder and having a piston rod secured thereto to project outwardly of said cylinder, a leg member pivotally connected at one end to said gantry, means pivotally connecting the projecting end of said piston rod to said leg member intermediate the ends of said leg member, the other end of said leg member having means whereby it may be connected to said counterweight so that said counterweight may be lifted and lowered, respectively, upon raising and lowering of said piston in said cylinder, and means extending serially between said gantry and leg member and the free end of said boom for raising and lowering said boom.

2. A machine of the character described having a chassis, and a frame pivotally mounted on said chassis for rotation about a vertiacl axis, a boom pivoted at one end to said frame at one side of said axis and having its opposite end free, a counterweight removably mounted on said frame at the opposite side of said vertical axis, a cylinder pivotally connected at its lower end to said frame at said opposite side of said axis but between said counterweight and said axis, a gantry secured to said frame between said boom and said cylinder, a piston reciprocable in said cylinder and having a piston-rod secured thereto projecting outwardly through the upper end of said cylinder, and a leg member pivotally connected at one end to said gantry at the top of said gantry and pivotally connected intermediate its ends to the projecting end of said piston rod, the other end of said leg member having means for connecting it to said counterweight whereby said counterweight may be lifted and lowered, respectively, upon raising and lowering of the piston in said cylinder, means extending serially between said gantry and said leg member and the free end of said boom for raising and lowering said boom, and means limiting movement of said piston rod outwardly of said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 2,189,212 Ljungkull Feb. 6, 1940 2,348,285 Ekbom May 9, 1944 2,411,305 Taylor et al Nov. 19, 1946 2,602,551 White July 8, 1952 2,689,655 Potter Sept. 21, 1954 FOREIGN PATENTS 675,747 Germany May 16, 1939 

